A robot for transferring a semiconductor wafer is conventionally well-known (for example, refer to Patent Document 1). A robot described in Patent Document 1 includes a column section that is cylindrical and able to move up and down, an arm whose root end side is connected to the column section so as to be rotatable, and a wafer grasping section (hand) that is connected to a top end side of the arm so as to be rotatable. Moreover, the robot includes a lifting mechanism for moving the column section up and down, a rotating mechanism for rotating the arm with respect to the column section, and an arm actuating mechanism for stretching/contracting the arm. The wafer grasping section is so formed as to be Y-shaped, and a transmission sensor including a light emitting part and a light receiving part is placed at a top end of the wafer grasping section.
In the case of the robot described in Patent Document 1, a teaching operation jig is used at a time of teaching the robot a position of a semiconductor wafer to be placed at a wafer placement position such as a storing container. The teaching operation jig is provided with a large disc part and a small disc part, wherein the large disc part and the small disc part are stacked in a vertical direction, in such a way that an axis center of the large disc part and an axis center of the small disc part are consistent with each other. Meanwhile, a diameter of the large disc part is the same as a diameter of an actual semiconductor wafer. The teaching operation jig is placed for use at the wafer placement position.
Moreover, at the time of teaching the robot a position of the semiconductor wafer to be placed at the wafer placement position, in the case of the robot described in Patent Document 1; at first while the wafer grasping section is moved vertically by use of the lifting mechanism, the transmission sensor detects a position of the small disc part, in a vertical direction, of the teaching operation jig placed at the wafer placement position. Then, while the wafer grasping section is brought closer to the small disc part from an outside in a radial direction of the small disc part, by use of the rotating mechanism and the arm actuating mechanism, the transmission sensor detects a position of an outside edge in the radial direction of the small disc part. Furthermore, the detecting operation is repeated by way of bringing the wafer grasping section closer to the small disc part from various directions. Then, on the basis of a plurality of positions of outside edges in the radial direction of the small disc part, wherein the outside edges being detected by the transmission sensor; a center position of the small disc part in a horizontal direction is detected. In the case of the robot described in Patent Document 1, on the basis of detection results with respect to the position of the small disc part of the teaching operation jig in the vertical direction and the center position of the small disc part of the teaching operation jig in the horizontal direction, the position of the semiconductor wafer to be placed at the wafer placement position is automatically taught.